Flask



FIG. 1 is a top plan view of a flask showing my new design;

FIG. 2 is a front, rear, and lateral elevational view thereof;

FIG. 3 is a perspective view thereof; and,

FIG. 4 is a bottom plan view thereof.

The broken line showing is included for the purpose of environment onlyand forms no part of the claimed design.

The ornamental design for a flask, as shown and described. 